Strange board upgrade in 512K

[Ih8reno]

Hi all

Today I thought I’d try and open up some of my macs and attempt to repair or simply clean them out. One of them is a strange one, it is a Mac whose serial # indicates it is a 128k but on the back it has a sticker with 512k.

I opened it up and saw this board soldered on as well as a lot of the memory chips were socketed. Is it safe to assume that it’s a non Apple upgrade? Also the Mac makes a high pitched squeak that never stops would it be related to this?

Also found this

 

[MacTech68]

That would be, as you suspect, a third party 512K upgrade on a 128K motherboard.

The squeal would be unrelated to this.

 

[Ih8reno]

That would be, as you suspect, a third party 512K upgrade on a 128K motherboard.

The squeal would be unrelated to this.

Thanks, figured. Any idea a little that constant High pitched noise?

 

[MacTech68]

Thanks, figured. Any idea a little that constant High pitched noise?

Got a recording ?

Could be FBT, or excessive load on PSU. Is the screen affected? Can you check & adjust +5 volt rail ?